The German utility model DE-GM-93 00 919 describes a movement control device for moving objects. A ball rests on the moving object and is driven by the linear movement of the object. Material embedments are provided on the circumference of the ball and generate, together with a signal device, the movement signals to be determined. In accordance with a modification of the invention, the material embedments have optical properties differing from the remaining surface of the ball and picked up by a reflected light barrier aligned with the surface of the ball.
EP-B-0 146 917 discloses a system for recognition of the presence of a transported article on the casing surface of a rotating transport element. Inside the casing of the transport element, two openings are provided for receiving the ends of an optical waveguide. The optical waveguides pass the optical information to a stationary component in which a light transmitter and a light receiver are accommodated. An evaluation circuit converts the signals into a control signal indicating the presence or absence of a transported article. It is here immediately clear to a person skilled in the art that the scanning of the surface of the rotating transport element from the inside is mechanically difficult and hence unnecessarily increases the cost of a transport element.
EP-A-0 653 688 shows that it is known for a roll (in this case a contact pressure roller against a fuser roller) to comprise at least two layers of differing materials. The roller comprises a deformable material and a harder outer shell or casing.